Retractable knife



FIG. 1 is a front perspective view showing my new design for aretractable knife according to the present invention;

FIG. 2 is a side elevational view thereof;

FIG. 3 is another side elevational view thereof opposite to that shownin FIG. 2;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a front end view thereof; and,

FIG. 7 is a rear end view.

The ornamental design for a retractable knife, as shown and described.